1. Field of the Invention
The present invention relates to engine exhaust temperature monitoring systems and, more particularly, to a selectively engaged recording system which is connected to record all instances of excessive exhaust temperature.
2. Description of the Prior Art
Monitoring of an exhaust manifold by way of various temperature sensors has been known in the past. Typically, the exhaust temperature of an engine, and particularly a diesel engine, can be increased by excess use of fuel. Continued use of an engine at abnormally high temperatures in addition to the loss in efficiency grossly decreases the life of many components thereof.
In fleet operations such as a commercial trucking fleet, extending the useful life of a diesel engine is often a significant economic factor. It is, however, normally possible to drive a truck at a constant speed at various fuel mixtures settings. Thus, an operator may have acquired improper habits and while still meeting schedules may be inadvertently overheating the engine. Since various employees assigned to any one truck in the fleet may have, by way of prior employment, acquired such improper driving habits, monitoring this critical parameter becomes important both for maintenance purposes and for the purpose of retraining the employees to more correct habits.
Since abnormal operation is not a continuing phenomenon, continued monitoring recording of this parameter would entail large costs both in the recording paper and in the subsequent necessary inspection of the records. Since generally any engine is designed for a particular thermal balance and will operate optimally when maintained within the balanced state, it is only the instance of excess that are of interest to any fleet owner.
In addition, while a continued over temperature operating condition may indicate improper driving habits, this same data is indicative of many other engine malfunctions and is therefore significant to preventive maintenance. Generally, sensing of the operating temperatures within an engine are best accomplished by monitoring the exhaust temperatures thereof. In the prior art, and in this invention, the use of a thermocouple as the monitoring instrument is the manifold provides the most economic means of reading out the temperature. Thermocouples, however, typically generate small signals and are subject to various sources of noise and drift, the most particular of which is the existance of ground differentials or ground loops within the vehicle.